I have decided in a few months after deployment to take out my engine out of my 1974 F350 Super Camper Special due to three cylinders are significantly under compression compared to their neighbors which is causing rough idle. Plus, with the engine reaching 100,000 miles and based on the year of the truck, I think remanufacturing is definitely recommended.

The engine is the original motor:

460 V8 7.5L attached to a 4 speed automatic transmission

Shop I found is capable of doing a full engine build, BUT, peaked my interest when they asked what do I intend to do with the truck? Ultimately, I definitely intend to install new headers, performance cam, intake manifold, MSD, upgrade to a double roller timing set, and potentially replace the transmission to a 5 maybe 6 speed. However, being fairly new to carbs, I was intrigued upon discovering blow through carbs and the setups involved.

So! Context is established, lets move on to the questions!

1. Is installing a blow through turbo system worth the power or are all the previous mentioned additions enough to make a difference? Believe stock HP is around 240, and according to Powernation.TV, component swaps like these will add roughly 100-110 HP to a naturally aspirated engine without impacting (too much) to fuel economy.

2. With a blow through setup installed, does my vehicle constitute as high performance street or racing?

3. What internal components should be changed in regards to ignition? Some say piston heads should be changed to handle the boost that stock can't accommodate to as well as the crankshaft.

4. Stock fuel efficiency is around 7-10 mpg (this old truck was a hauler). If converted to blow through, at cruising speeds, what should or might I expect to see as far as MPG efficiency?

Note: Engine bay as a lot of potential once I remove the window washer pump, container, auxiliary battery, and potentially the AC condenser and compressor (to install the intercooler in front of radiator). All things I can live without.

These are my immediate thoughts, and I definitely intend to post pictures of my current engine bay and restorations that follow in respects to if I proceed to go with the blow through installation. If you have any insight or comments, I'd greatly appreciate them. Thanks in advance!

 

How much hp are you looking to make? You can make a lot of power with a properly setup turbo system. The only thing you should do while it’s at the machine shop is have them open up the ring gaps.With a blowthru carb you will not get the fuel mileage of an efi setup. What trans?They didn’t have a 4speed auto from the factory.

 

I probably would skip the blow thru carb and spend the money on a Holley Sniper EFI. It bolts in place of the carb so you can still use your intake, and you will have EFI drivability and mileage.

 

Turbo it (this forum isn't going to tell you otherwise), the gains from FI are going to be much better bang for the buck than any basic bolt on package. Use one of the Fitech power adder units or sniper EFI.
There is no off the shelf turbo kit for these, you will have to build it yourself or have it custom made.
The only factory 5 speed manual that will bolt up to these is the big block zf5, it will not handle turbo power. you could get a T56 and bellhousing if you want a manual but it wont be cheap. A C6 auto will handle the power with nothing but a shift kit, you can add a gear vendors to get overdrive.
For the rebuild I would get forged pistons at a minimum, the stock cast ones don't hold up to boost, the stock rods will be ok to 600hp, as long as you keep the rpm under 6k. If you get over that HP, or want to spin it harder you will want forged rods.
There are several 460 builds on this forum, at least 3 on that platform pickup, start reading them and you will get an idea of what you want from the turbo kit.

 

I did this with a stock freshened 460 in a 1974 trailer special. Put a holley super sniper efi on it and a s475 turbo and didnt bother much with checking the Wastegate springs. Test drove it a few times and shattered 2 pistons on my first 2nd-3rd gear pull. Saw over 26psi was sketchy doing burnouts at above 90mph. I would think 12-14 pounds and it would've lived a long life.

I'm starting to put the parts together for a 545ci deal with probably a pair of the s475's.

Long story short , do it. But make sure you dont just send it like I did lol.

 

My stock "car" rod short block took 10 psi on e85 blowthru for a whole season. Never broke it.
Even 5 psi was a pretty big performance jump

 

Did you pull the timing back during the torque curve ?

 

I did. I was using msd 6530 and had it pulled back 1 for 1 past a couple pounds. I thought it had to of detonated, when I pulled the heads it had chunked 1 piston on each bank. Maybe the rings butted and cracked them I'm not sure.

 

Thats likely, I had that happen on one 460. They have big bores so the gaps get tight in a hurry under boost.

 

It was amazing the kind of power it was making though. I'm hooked and am building this next one to be a lot more put together than slapped together lol